1. Field of the Invention
The present invention is concerned with new anti-reflective compositions for use in photolithographic and semi-conductor integrated circuit manufacturing. In particular, the compositions are used as bottom anti-reflective coatings located beneath a photoresist layer to minimize interference from the reflection of applied light radiation.
2. Description of the Prior Art
Integrated circuit manufacturers are consistently seeking to maximize substrate wafer sizes and minimize device feature dimensions in order to improve yield, reduce unit case, and increase on-chip computing power. As the critical dimensions of integrated circuits have decreased, the wavelength of the radiation used to expose photoresists has similarly shortened. The use of shorter wavelength radiation is necessary to define the very small features of a circuit, and typically so-called i-line radiation with a wavelength of 365 nm is now used. A consequence of the use of such radiation is an increasing reflection of the radiation at the interface of the photoresist layer and the underlying layer, giving rise to standing waves which can cause undesirable variations in the critical dimensions of circuit features.
One approach to address this problem is the use of an anti-reflective coating applied to the substrate beneath the photoresist layer. These can be divided into two classes—inorganic and organic. Inorganic coatings, such as titanium nitride or silicon oxynitride coatings, can be deposited easily by plasma-enhanced chemical vapor deposition but can be difficult to remove from a silicon wafer substrate. In contrast, organic coatings are advantageous in terms of refractive index, spin-on application, and rework capabilities but often suffer from spin bowl incompatibility, thus requiring additional processing and increased manufacturing costs. While both organic and inorganic anti-reflective coatings are effective at preventing or minimizing reflection, their use requires an additional break-through step in the process in order to remove the coatings. Typically, an additional plasma etch step is then required which can further significantly increase the cost of the manufacturing process.
One solution to this problem has been the use of wet developable anti-reflective coatings. These types of coatings can be removed along with the exposed areas of the photoresist material. That is, after the photoresist layer is exposed to light through a patterned mask, the exposed areas of the photoresist are wet developable and are subsequently removed with an aqueous developer to leave behind the desired trench and hole pattern. Wet developable anti-reflective coatings are removed during this developing step, thus eliminating the need for an additional removal step. Unfortunately, wet developable anti-reflective coatings have not seen widespread use due to the fact that they must also exhibit good spin bowl compatibility and superior optical properties to be useful as an anti-reflective coating. Thus, there is a need for anti-reflective coating compositions which are developable in conventional photoresist developers while simultaneously exhibiting good coating and optical properties and being spin bowl compatible.